Smithsonian.com

Humans clearly have a sweet tooth, but now that high-calorie food is available to many people with little physical effort, obesity rates are skyrocketing.

Fast food isn't the only factor in rising obesity rates. Anthropologists are now studying why we eat certain things, rather than just what we eat. Image courtesy of Flickr user VirtualErn.

In a recent issue of AnthroNotes, produced by Smithsonian’s National Museum of Natural History, anthropologists Peter J. Brown and Jennifer Sweeney use culture to explore the behaviors and beliefs in societies that influence weight.

They start out by reviewing why humans crave sweet and fatty foods. Calorically dense foods were rare in the pre-agricultural world, where prey animals often carried little extra fat and natural sugars (like honey or ripe fruit) were rare. We seem to be genetically predisposed to eat higher calorie foods to store energy.

When it comes to weight today, Brown and Sweeney note that there are fundamental flaws in the measures of obesity, like the body mass index (BMI), because food preferences and other shaped habits aren’t taken into account.

For example, a BMI greater than 30 is defined as obese. But the researchers note that muscular athletes tend to have high BMIs because muscle weighs more than fat. Also, BMI does not account for the distribution of fat on the body. Body fat in the central areas of the body is more likely to be associated with cardiovascular disease, whereas fat in the hips and limbs does not carry the same risk.

However, the most interesting part of this study (at least to me) was their discussion of the cultural perceptions of weight, particularly among women. Brown and Sweeney write:

An important recent ethnography of Azawagh Arabs of Niger entitled Feeding Desire (Popenoe, 2004) illustrates these cultural notions to an extreme degree. Here, fatness to the point of voluptuous immobility is encouraged by systematic over-eating in order to hasten puberty, enhance sexuality, and ripen girls for marriage. The people believe that women’s bodies should be fleshy and laced with stretch-marks in order to contrast with thin, male bodies.

Men, too, feel the need to gain weight in some cultures. The study cites names like “Notorious B.I.G., Heavy D and the Fat Boys” as examples of culturally accepted icons that are obese, promoting the idea that men need to be large to have power and respect.

All of this leads up to the study’s conclusion, which states emphatically that health officials must understand and take into account cultural causes of obesity if they want to effectively address the obesity problem. Otherwise, messages will be misinterpreted, like this obesity prevention ad in a Zulu community.

It featured one health education poster that depicted an obese woman and an overloaded truck with a flat tire, with a caption “Both carry too much weight.”… The intended message of these posters was misinterpreted by the community because of a cultural connection between obesity and social status. The woman in the first poster was perceived to be rich and happy, since she was not only fat but had a truck overflowing with her possessions. (Gampel 1962)

Ghrelin has no resemblance to this gremlin, courtesy of Flickr user inti

Scientists have known for several years now that people are partly controlled by the gremlins and goats in their stomachs…

Pardon me, I mean ghrelin, the so-called “hunger hormone” that triggers appetite when it interacts with fatty acids in the stomach, and GOAT, the enzyme that facilitates that interaction. (But when I’m really hungry, I could swear there are a few of those other creatures kicking around in my belly, too!)

Until now, it’s been assumed that the fatty acids which activate ghrelin are something the body produces when we’re not eating, meaning that hunger is inevitably triggered by an empty stomach. Turns out that may not be the case, however. Instead, it seems to be ingested dietary fats that activate ghrelin—in other words, eating a deep-fried Twinkie may actually make you hungrier! (Or, to put it visually…)

This twist comes from a new study in the journal Nature Medicine, conducted by the University of Cincinnati’s Matthias Tschöp and other scientists. Their findings “turn the current model about ghrelin on its head,” at least according to the press release.

Reporting evidence that “ghrelin is acting more as a meal preparation cue than as a hunger cue,” the study’s authors posit that “GOAT-ghrelin system acts as a nutrient sensor by using readily absorbable [fatty acids] to signal to the brain that highly caloric food is available, leading to optimization of nutrient partitioning and growth signals.”

The study was conducted in mice, so it’s premature to draw conclusions about humans from it, but the possibilities are intriguing in terms of treating metabolic disorders and obesity.

It may also explain why gastric bypass surgery is so successful in curbing appetite, as Tschöp notes: “This procedure causes food to bypass the stomach and gut sections that contain GOAT/ghrelin cells, which, based on this newly described model, would prevent ghrelin activation.”

I think my gremlin wants salad for lunch today.

Sugarcanes are 90% juice, and almost one-fifth of the juice is straight sucrose. Image: R. Uribe/Wikipedia

Should sugar be a controlled substance? For the love of honey, no! Dietitians can take away my trans fats and feed me one percent milk, but show mercy and leave me my sugar. Sugar is the most basic food there is. As a molecule, it’s one of the world’s most fundamental. It’s the first incarnation of any organic substance, born inside a leaf from carbon dioxide, sunlight, and water. During digestion, it’s also the final incarnation of our food (no matter what we had for supper) before our cells burn it for energy.

But if sugar is so simple, why are Twinkie packages so hard to read? Why are snacks, desserts, condiments, and TV dinners stuffed with so many sweetening agents? For that matter, why do those health-store, honey-sweetened cookies have that thin, slightly tinny taste that sugary cookies lack?

The answer, of course, is that sugars come in many varieties. The variations are minute—look at a molecular diagram and you’d be hard pressed to pick one from another—but they impart stark differences in taste and cooking behavior. That’s why we need just the right combination to get that Twinkie to taste right.

So here’s a breakdown of the common sugars and where you might find them. Use it for reference, or for sweet reflection (many thanks to Harold McGee and Alan Davidson):

Glucose (also called dextrose): The simplest sugar (but weirdly one of the least sweet), this is what your cells burn for energy. When plants or animals need to store glucose, they stack the molecules into long chains to make starch. Like all sugars, glucose contains only carbon, hydrogen, and oxygen. Glucose is shaped more or less like a single hexagonal ring, so it’s called a monosaccharide.

Fructose has exactly the same number and type of atoms as glucose, just arranged differently. This slight change makes fructose about twice as sweet as glucose. Fructose is the main sugar you find in honey, giving it its almost jarring sweetness. Some clever people have realized that baking with doubly sweet fructose means you can make treats with half the sugar calories of glucose. Remarkably, though, fructose molecules change shape and lose much of their sweetness when they are hot, so this trick doesn’t work in sweetening tea or coffee.

Sucrose is the most common sugar made by plants, and it’s the molecule we extract from sugarcane or sugar beets and turn into table sugar. It consists of one fructose molecule joined to one glucose molecule. That’s two rings, so sucrose is referred to as a disaccharide. We all love sucrose (if not quite as much as John Travolta did when he played that annoying angel in Michael). And conveniently for our tongues if not our waistlines, it remains delicious even at very high concentrations.

Maltose, found in malt extract, and lactose, found in milk, are two more disaccharides that are much less sweet than sucrose or fructose.

High fructose corn syrup is what we get when we cook down the starches from corn kernels to liberate the sugars they contain. About 75 percent fructose and the rest glucose, it’s about as sweet as table sugar. And because American corn is so cheap (artificially, as Michael Pollan has pointed out), it has become ubiquitous as an industrial-scale food sweetener.

Maltodextrin is another variety of processed corn syrup—in some respects another way to sneak sugar onto a wrapper’s ingredient list without raising a consumer’s eyebrows. A combination of glucose and maltose, maltodextrin is chewy and not particularly sweet.

Oligosaccharides are sugars consisting of more than two hexagonal rings, found in beans and other seeds. The neat thing about oligosaccharides is that animals can’t digest them, but the bacteria in our intestines often can—leading to those remarkable intestinal chemistry experiments that sometimes happen after a meal of legumes.

This list doesn’t touch the artificial sweeteners—like the Stevia Amanda wrote about. They all contain some non-sugar substance that tricks our tongues into registering sweetness. Other tricksters include artichokes, which briefly disable our sweet receptors so whatever we eat next seems sweet, as well as the really weird miracle berry, which can discombobulate your tongue for a few hours at a time.

Artificial sweeteners promise the impossible: they’re hundreds of times sweeter than sucrose but contain negligible calories. If only taste were that simple. I’ve never had a zero-calorie dessert that could compare to the simple sucrose rush of chewing on a stalk of sugarcane. I’m supporting freedom for sugar in 2009!

(Note to Amanda: a cwt seems to be short for a hundredweight. Which is 100 pounds in the U.S. and 112 pounds in Britain. Can the “c” really be a holdover from the Roman numeral 100? Good old imperial measurement system.)

Most of us eat too much during the winter holidays—even though we know that all those latkes, lefse, or gingerbread men can linger around our waistlines well into the new year. It’s easy to see why advertisements abound for “easy weight loss” products. But is there such a thing?

Perhaps it’s no coincidence that the FDA chose late December to issue a consumer warning about tainted weight-loss pills. Apparently, many of the so-called natural weight-loss remedies now on the market contain “undeclared active pharmaceutical ingredients” that pose health risks for consumers. Some ingredients, like rimonabant, are not FDA-approved for marketing in the United States, while others are approved for a very different purpose—phenytoin, used in “3X Slimming Power” and “Extrim Plus,” is actually an anti-seizure medication. And phenolphthalein, found in at least eight brands of weight-loss pills, is a suspected carcinogen. Sibutramine, present in nearly every brand of pill on the FDA’s list, is a powerful appetite suppressant that is approved only for prescription use (brand name Meridia) because it can cause serious increases in blood pressure and heart rate.

Many herbal supplements, like chitosan or guar gum, have proven unlikely to cause weight loss, and can cause unpleasant side effects like constipation, flatulence, and bloating. Green tea extract might boost metabolism and curb the appetite, but at the cost of similarly nasty side effects.

Though the shocking prevalence of obesity in America is a relatively recent trend, the hunger for an easy cure dates back at least a century:

“It is all a matter of food,” declared a 1904 Chicago Tribune article titled “How to Get Fat or Thin.”

The author explains the differences between carbohydrates (”fuel foods”), protein and fat, and offers this advice: “If anybody who finds himself or herself beginning to get too fat will simply give up potatoes and bread for a while, the tendency will promptly cease… As for meats (if lean), as well as eggs, they are muscle and blood makers, and could never contribute fat to the most corpulently inclined individual.”

Hmm…sounds like the Atkins’ diet has been around for a long time. (Sorry to report that it, too, comes with some unappetizing side effects.)

The best strategy, of course, is simply to know what your body needs and eat accordingly. And in case you needed a little extra motivation, consider that Tribune writer’s closing argument: “How many old people do you know who are overfat?…The reason is that corpulent persons rarely reach old age; they die first.”

Um…happy new year?

News flash: Fast food is bad for you!

Okay, you probably already knew that. But in a recession like this, isn’t it tempting to bite at anything labeled “value?”

I just noticed on one of my favorite food blogs, The Food Section, that a DC-based nonprofit called the Cancer Project published a report this week picking on the negative nutritional value of items on fast-food “value menus.” It ranks the worst offenders: a junior bacon cheeseburger from Jack-in-the-Box tops the list, followed by Taco Bell’s cheesy double beef burrito. McDonald’s, Burger King and Wendy’s all take a hit as well.

The rankings were based on familiar factors including high fat, sodium, cholesterol and total caloric content, low fiber, and lack of fruits and vegetables (no, pickles don’t count). The top-five worst culprits, priced at less than two bucks, contain on average 396 calories, 21 grams of fat, and more than 1,000 mg of sodium. Nothing junior about that.

Perhaps more controversially, the Cancer Project researchers also demoted menu items that included dairy products, which it says elevates the body’s level of a cancer-causing hormone. But there are plenty of conflicting studies out there about the cancer-dairy connection, and dairy is a good source of calcium and vitamin D, which may lower the risk of colorectal cancer. Oh, but wait, that depends on if you eat it as a child or an adult … I’m confused, but it seems like we shouldn’t throw the cheese out with the burger just yet.

The Cancer Project’s value-menu study brings up a good point, though: There’s a clear link between nutrition and socioeconomic status. I bet a lot of the people buying those 99-cent bacon burgers know very well they’re not eating something healthy. But I would also bet they can’t afford—in terms of money, or time—to shop for $8-a-pound organic grass-fed beef and $5 turkey bacon at upscale grocery stores like Whole Foods and take it home to cook. (To its credit, Whole Foods is now offering a list of “budget-conscious recipes” and “money-saving tips” on its Website. It claims these low-fat turkey burgers can be made for less than $3 a person, but you do need a grill.)

For folks in the middle like me, it’s a balancing act: I don’t eat fast-food, period. But I do pay attention to coupons, sales, and “unit prices” at the grocery store. I’ll shell out more for organic vegetables or whole-grain bread, but mix those items with cheaper products like generic beans or pasta. One of my favorite lunches is simply to mix up some canned chickpeas, steamed broccoli florets and fat-free Italian salad dressing. That breaks down to pennies a day, and it’s very healthy.

What’s on your personal “value menu?”